The present invention relates to a cassette holder device for tape recorders, and particularly to a cassette holder device which is adapted for receiving two kinds of cassettes, that is large size cassettes and small size cassettes.
A conventional cassette holder device having a mechanism for preventing an erroneous insertion of a cassette tape will be described below by referring to the drawings.
FIG. 8 is a rear side view of a large size cassette tape (hereinafter, referred to simply to a large size cassette). In the figure, a large size cassette 1 is formed with a guide groove 2 on its rear surface and includes a supply reel 3 and a take-up reel 4.
FIG. 9 is a rear side view of a small size cassette tape (hereinafter, referred to simply as a small size cassette). In the figure, a small size cassette 5 is formed with a guide groove 6 on its rear surface and includes a supply reel 7 and a take-up reel 8.
FIGS. 10A and 10B show a positional relation between large size cassette 1 and small size cassette 5 in a cassette holder. From these figures, it is seen that, when the left side edges of large size cassette 1 and of small size cassette 5 are aligned with each other, the positions of guide grooves 2 and 6 are also coincident with each other.
FIG. 12 and FIG. 13 show perspective views of large size cassette and small size cassette, respectively. In FIG. 12, the two reels contained in large size cassette 1 of a box shape include respective flanges 29 and 30. A lid 31 for normally covering a tape stretching portion on the front surface of cassette is urged in a lid closing direction by means of a spring (not shown), and is formed with a slant surface 31b on the upper front portion thereof. Grip grooves 32 and 33 are formed in rear side surfaces of large size cassette 1. In FIG. 13, the reels contained in small size cassette 5 have respective flanges 35 and 36. Grip grooves 37 and 38 are formed on rear side surfaces of small size cassette 5. Further, a front lid 39 for protecting the tape stretching on cassette front surface and a rear lid 40 for similarly protecting the tape stretching portion are provided and are urged in lid closing directions by means of respective springs (not shown). Front lid 39 is formed with a slant surface 39a on its upper front portion, and a step portion 40a is defined by front lid 39 and rear lid 40.
FIGS. 11A and 11B show a conventional cassette holder. In the figure, numeral 9 denotes a cassette holder member for accommodating large size cassette 1 or small size cassette 5 so as to supply and receive each of them and from an apparatus such as a video tape recorder (not shown). On cassette holder member 9 is fixed a guide member 11 by caulking, for guiding a cassette when a cassette is inserted, and preventing erroneous insertion of the cassette. On the upper portion of cassette holder member 9 is screwed a top plate 10, thereby forming a box shape as a whole. On the upper side of top plate 10, there are provided three mechanisms for preventing large size cassette 1 or small size cassette 5 from floating up when loaded in the body of an apparatus. The first mechanism is a cassette urging lever 12 swingable about a pin 13 and downwardly urged by means of a spring 14. The second mechanism comprises a cassette urging lever 15 located at a position corresponding to the left upper portion of large size cassette 1 or small size cassette 5. Cassette urging lever 15 of this second mechanism is also swingable about a pin 16 and downwardly urged by means of a spring 17. The third mechanism is a cassette urging lever 18 located at a position corresponding to the substantially central portion of large size cassette 1 and to the right upper portion of small size cassette 5. Cassette urging lever 18 is swingable about a pin 19 and downwardly urged by means of a spring 20. A roller 21 is located at a position corresponding to the upper portion of large size cassette 1 or small size cassette 5 and rotatably supported by a lever 18 through the intermediary of a pin 22. Among cassette stoppers 25, 26, and 27, the stoppers 25 and 26 are formed integrally with cassette holder 9, while the stopper 27 is a separate member fixed to cassette holder 9 by cauking a pin. These stoppers 25, 26, and 27 limit the insertion extent of the cassettes.
The cassette 1 or 5 is, when loaded into the apparatus not shown, supported by reference pins provided on a chassis and adapted to engage with reels 3 and 4 in large size cassette or reels 7 and 8 in small size cassette 5, and is pushed downwards against these reference pins by cassette retaining levers 12, 15 and cassette retaining roller 21 with the lower surface of the cassette apart from the chassis. Thus, cassettes can be positioned and holded. Accordingly, the opening of cassette holder member 9 for introducing cassette 1 or 5 has a hight greater than the depth of cassette 1 or 5.
As mentioned above, in a cassette holder device of prior art, whether cassette insertion is correct or erroneous is judged by whether the engagement between guide groove 2 or 6 formed in the lower surface of cassette and cassette guide 11 fixed to cassette holder member 9 is normal or not. Namely, in case of erroneous insertion of a cassette, the insertion is impossible because of an erroneous insertion of a cassette, the insertion is impossible because of abutting of the cassette side surface against the tip of cassette guide 11.
However, in the conventional device, in order to surely preventing erroneous insertion of a cassette, it is required to make the depth of guide groove 2 or 6 deeper and the hight of cassette guide 11 higher for producing an engagement between the cassette side surface and the cassette guide in a wide range. These structural features cause an increased depth of cassette, because the provision of a deeper guide groove is required in a cassette in addition to reels for winding a tape. On the other hand, it is desired to make the depth of cassette minimum for assuring an easier handling and a convenient storing of a cassette.
As mentioned above, in the prior art there is a restriction on minimizing the depth of guide groove 2, 6 and the depth of cassette guide 11. Upon erroneous insertion of cassette by a great force, it may happen for the cassette to be pushed by force with the cassette riding on cassette guide 11 due to the above-mentioned rather wide clearance between the size of the cassette insertion opening of cassette holder member 9 and the size of the cassette, or due to deformation of the bottom surface of the cassette holder member 9 (on which cassette guide 11 is disposed). In such erroneous operation, it become difficult to take out the forcedly inserted cassette, and further, when an operation for loading the cassette holder member 9 into the recorder apparatus is carried out in force, there may be occur destructions of the cassette holder and even the apparatus body, because the cassette holder member can not be engaged correctly with reel beds or tape guide post (not shown) both arranged in the apparatus body.
A cassette frame is, in general, made from a plastic material by molding process, and is inferior in strength at the central portion thereof due to the structural feature of the frame. The top plate 10 of the shown prior art includes three cassette retainers 12, 15, and 18 for urging large size cassette 1 or small size cassette 5 against the chassis.
In this arrangement, when a large size cassette is used, the cassette urging roller 21 for pushing the right upper portion of a small size cassette 5 abuts against a part near the central portion of large cassette 1 where the strength of cassette 1 is inferior. This pushing force of roller 21 causes deformation of cassette 1 and inclination of a guide post arranged in the cassette, thereby finally giving an adverse effect on the running of tape.
When a cassette is loaded into the apparatus body, lids 31, 39 provided on the cassette are required to be opened against the spring forces usually urging the lids to their closed position. These spring forces act on the cassette in a direction opposite to the cassette insertion direction, thereby causing a risk that the cassette is not inserted into a regular position. As mentioned before, a cassette is required to be inserted to a position defined by stopper 25, 26, 27. A positional deviation of the cassette in the above-mentioned opposite direction may cause an adverse effect on the tape running, because the cassette is not located in a correct position in the apparatus when the cassette holder is loaded into the apparatus. For preventing a positional deviation of a cassette, there are provided rather greater pushing forces for pushing cassette retaining levers 12, 15 and cassette urging roller 21. However, this solution has a disadvantage that the force required for insertion of cassette become greater accompanied by an insertion feeling uncomfortable. Further, when a small size cassette is no fully inserted into the holder with its rear edge not abutting against stoppers 26 and 27, destructions of the apparatus body and the cassette may be caused. In addition, due to the frictional sliding between the upper surface of the cassette and the retaining levers 12 and 15, the surface of the cassette suffers scratches, and the swarf produced thereby may fall into the inside of the apparatus body, possibly causing dropouts of some of reproduced signals.
Further, since the cassette is required to be formed with a guiding groove 6 on its lower surface, the strength of the cassette is decreased and distortion in a molding process are apt to be caused, thereby deteriorating appearance and shape accuracy of the cassette. In addition, as mentioned before, the thickness of the cassette become greater due to the guide groove, resulting in a disadvantageous cassette size.